UV vs sunray

UV and sunray both are nouns.

Word	Noun	Adjective	Verb	Adverb
UV	Yes	No	No	No
sunray	Yes	No	No	No

As nouns, sunray is a hyponym of UV; that is, sunray is a word with a more specific, narrower meaning than UV:

UV: radiation lying in the ultraviolet range; wave lengths shorter than light but longer than X rays
sunray: a ray of artificial ultraviolet light from a sunray lamp

Other hyponyms of UV include sun-ray.

UV (noun)	sunray (noun)
radiation lying in the ultraviolet range; wave lengths shorter than light but longer than X rays	a ray of sunlight
	a ray of artificial ultraviolet light from a sunray lamp
	herb having a basal cluster of grey-green leaves and leafless stalks each with a solitary broad yellow flower head; desert areas Idaho to Arizona